Novel, high-yielding lettuce phenotype generated by urea amine nitrogen nutrition displays contrasting traits to those of nitrate- or ammonium-fertilized plants

Abstract

Fertilizing intact plants with particular forms of nitrogen (N), at equal concentrations of total N, gives rise to N-form-specific morphological and physiological phenotypes. Urea amine nitrogen is only transiently available in soil, thus its effects on plants have not been as well-defined. By stabilizing the N source urea amine, we have begun to characterize a third phenotype in addition to those recognized for nitrate and ammonium. We show that non-limiting rates of stabilized amine nitrogen (SAN) induce specific traits in greenhouse-grown lettuce, that lead to increased yields compared to controls treated with conventional industry standard fertilizers, un-stabilized urea, calcium nitrate or ammonium nitrate. These were supplied at the same total weight of N, via the soil or foliarly, to seedlings of Lactuca sativa L. cv ‘Tom Thumb’ and/or ‘Lollo Rosso’. Initially tap root length, lateral root development and leaf chlorophyll content are increased by SAN. As plants mature, leaf biomass increases at a faster rate under SAN nutrition, and larger harvest weights are finally attained, and/or a given head weight is achieved more rapidly. We conclude that plants respond positively to the maintenance of nitrogen in ureic-amine form, by initially partitioning more biomass to roots whilst increasing photosynthesis. These changes allow provision of more soil-sourced and carbon-based resources to the leaves of maturing plants. Leafy vegetable yields can be increased using stabilized urea amine fertilizer. We identify proxy traits for yield in young seedlings, which could be utilized in breeding and phenotyping programs for a wide range of species.